1. Field of the Invention
The present invention relates to a handover method for an IP-based next generation mobile communication system network.
2. Description of the Related Art
Next generation mobile communication system networks currently in development employ an integrated wireless telephone and Internet Protocol (IP) network. It is expected that the next-generation system will seamlessly integrate the wireless telephone network with the IP network.
Accordingly, in the next generation mobile communication system networks, Layer 3 handover (handover for routing in the IP network) is important for proper operation, as is Layer 2 handover (handover between base stations in the wireless telephone network), both of which have attracted attention in conventional wireless telephone networks.
FIG. 1 is a view for explaining a cell group for handover in the conventional next generation mobile communication system.
The conventional next generation mobile communication system includes an access router 1 (AR 1) 10 and an access router 2 (AR2) 11 for routing in an IP network. The ARs 10 and 11 include a plurality of access points (APs), each of which controls one cell. Each AP provides services for a mobile terminal (MT) 13 located in a cell controlled by the AP.
In the conventional next generation mobile communication system, AR areas are divided in the same manner as AP groups are divided as shown by line 100 in FIG. 1. Accordingly, L2 handover between APs and L3 handover between ARs are performed at the same time.
As described above, each of the ARs relates to an individual network constructed by binding a plurality of cells into a cell group. Herein, only L2 handover is performed when the MT moves in each cell group, and the L2 handover of the APs and the L3 handover between the ARs are performed at the same time when the MT moves between cell groups.
FIG. 2 is a flowchart showing the handover process in the conventional next generation mobile communication system.
If the MT 13 moves (step 201), it is determined whether or not the mobile terminal 13 has left a predetermined AP area (step 202). Referring to FIG. 1, it is determined whether or not the MT 13 of an AP 101 has moved to another AP.
Thereafter, if the MT 13 has left the predetermined AP area, it is determined whether or not the MT 13 has left an AR area (step 203). Referring to FIG. 1, it is determined whether or not the MT 13 of the AP 101 has moved to an AP 111 in another AR area.
If it is determined that the MT 13 has left the AR area in step 203 (i.e., if the MT 13 moves to the AP 111 shown in FIG. 1), the MT 13 performs L3 handover between ARs and L2 handover between APs at the same time (step 205).
If, however, it is determined that the MT 13 has not left the AR area in step 203 (i.e., if the MT 13 moves to another AP in the same AR area and not the AP 111 shown in FIG. 1), the L2 handover between APs is performed (step 204).
When the above mobile IP technique is employed and the L2 handover and the L3 handover are performed at the same time, data is not transmitted until the L3 and L2 handover is complete since the L3 handover has signaling delay time longer than that of the L2 handover.
Additionally, in the next generation mobile communication network, since each cell radius becomes smaller than a present cell radius according to increase of band frequency, handover occurs more frequently. In particular, if the L2 handover and the L3 handover are done repeatedly in overlapping areas where movement between areas frequently occurs, it is impossible to efficiently transmit data.
In addition, since each handover is achieved through signaling messages over a radio link, such simultaneous support for both the L2 and L3 handover creates excessive in the signaling messages, and wasting radio resources.